When working in a team you *must* use some kind of revision control sytem. Examples of such systems are SVN, CVS, Perforce & Sourcesafe. Here at the office we use SVN. As client software we choose to use TortoiseSVN. I guess we are not alone using this great piece of software since to date there have been roughly 16,000,000 downloads of it.
Now, I have had a problem in the past. I often work on several differnet computers and often when you work on some piece of a game engine, it might take a couple of days, weeks, before something is ready (stable enough) to be commited to the revision control repository. But since I might start work on something on my laptop in the office, I want to continue the work at my stationary computer at home. I DO want to keep the files synchronized but I do not want to commit my changes to the repository since no other should be bothered with temporary/broken/test - code.
Previously I have synchronized manually. Moving files back and forth on a USB stick. This can really be a pain since it's hard to keep track of changes, and newly added files. It's no fun at all I tell you. And when I'm in a hurry, I always seem to forget at file or two. One exciting new piece of software which can help you a great deal in this situation is DropBox. It gives you 2GB of free server space, and it automatically tracks changes to files. You can use it as a simple revision control system or backup software. Whenever I add/change files in my "DropBox folder" the files get synced on the server and when I log in on my other computer I get all the changes automatically. It works really well.